The present invention relates to a cDNA clone, designated to icc13 (incompatible Capsicum annuun-Colletotrichum gloeosporioides interactions) gene and individual component; thereof including its coding region and its gene product; modification thereto; application of said gene, coding region and modifications thereto; DNA construct, vectors and transformed plants each comprising the gene or part thereof.
Plants are continuously threatened by fungi and other microbial pathogens and deploy a number of strategies to defend them against pathogen infection. The defense responses are complex and include the formation of antimicrobial phytoalexins (Van Etten et al., 1989) and pathogenesis-related (PR) proteins (Linthorst, 1991; Ponstein et al., 1994), and the deposition of lignin to cell wall (Dean and Kuc, 1988). One of the most efficient ways of disease resistant reactions against potential pathogens is the hypersensitive reaction (HR). HR prevents further invasion and colonization of pathogens, which is known to be incompatible interactions between plant and pathogen (Goodman and Novacky, 1994).
Fruit ripening represents a genetically synchronized system that involves development unique to plant species. The phenomenon of ripening includes changes in color, texture, respiration rates, flavor, and aroma (Giovannoni, 1993). Generally, ripe fruit increases susceptibility to pathogen infection (Prusky et al., 1991; Swinburn, 1983). Therefore, fruits as one of the reproductive organs of plants need protection against pathogens to maintain fruit integrity and seed maturation. The expression of PR proteins is developmentally regulated during the formation of flower and fruit (Neal et al., 1990; Tattersall et al., 1997). Recently, several antifungal proteins that are responsible for protection against pathogens during fruit ripening were identified (Fils-Lycaon et al., 1996; Meyer et al., 1996; Salzman et al., 1998).
Colletotrichuin gloeosporioides (Penz.) is the casual agent of anthracnose diseases on fruit crops (Daykin, 1984; Dodd et al., 1991; Prusky et al., 1991) such as pepper (Capsicum annuuin L.) (Kim et al., 1986; Manandhar et al, 1995). In order to successfully infect the host plants, the fungus produces the appressorium from the germinating conidium. Subsequently, an infection hypha from the appressorium penetrates the cuticle and epidermal cell of the host surfaces. In Colletotrichum fungi, the topography of the plant surface was thought to be a physical signal for inducing the appressorial formation (Staples and Macko, 1980). The surface wax of avocado fruit was reported to act as a chemical signal for the appressorial formation in C. gloeosporioides (Podila et al., 1993). The genes expressed during the appressorium formation of C. gloeosporioides induced by the host surface wax were cloned (Hwang and Kollatukudy, 1995). However, plant responses to the formation of appressorium and infection hypha of the fungus has not been studied.
In our previous study, we found that an isolate of C. gloeosporioides showed the incompatible interactions with ripe-red pepper fruit and the compatible interactions with unripe-mature-green fruit (Oh et al., 1998). To investigate the molecular mechanism involved in the incompatible interactions between pepper and C. gloeosporioides, we isolated the icc13 cDNA that is specifically expressed in the ripe fruit of pepper, but not in the unripe fruit, using mRNA differential display method. The expression of icc13 gene was studied based on fungal morphogenesis in the initial infection process during the incompatible interactions. We also found that the icc13 mRNA is induced by wounding and exogenous jasmonic acid during ripening.